1. Field of the Invention
This disclosure relates to controlling transportation of data packets, and in particular, but not exclusively, to control of data packets via a node provided with a filtering function.
2. Description of the Related Art
A communication system can be seen as a facility that enables communication sessions between two or more entities such as user equipment and/or other nodes associated with the system. Establishment of a communication session enables a user to be provided with various services. The communication may comprise, for example, communication of voice, video or other audio and/or image data, multimedia or any other data. A session may, for example, comprise a two-way telephone call or multi-way conference session or connection between a user equipment and an application server (AS), such as a service provider server or a proxy.
A communication system typically operates in accordance with a given standard or specification which sets out what the various entities associated with the communication system are permitted to do and how that should be achieved. For example, the standard or specification may define if the user, or more precisely, user equipment is provided with a circuit switched service and/or a packet switched service. Communication protocols and/or parameters which shall be used for the connection may also be defined. In other words, a specific set of “rules” on which the communication can be based on needs to be defined to enable communication by means of the system.
Signalling is an example of functions that is commonly defined in an appropriate communication protocol or protocols. Signalling between various entities associated with a communication session is typically required in order to control the communication session. Control is typically required for the set-up of the communication session and also later on during communication on the established communication session.
The communication may be provided by fixed line and/or wireless communication interfaces. Examples of fixed line systems include a public switched telephone network (PSTN), a local area network (LAN) and any other data network provided by means of fixed connections between the nodes thereof. The wireless communication may be provided, for example, by means of a mobile communication system or wireless local area networks (WLANs). Mobile communication systems refers generally to any telecommunications systems which enable a wireless communication when users are moving within the service area of the system. An example of a typical mobile communication system is a Public Land Mobile Network (PLMN).
The mobile communications network can provide an access network providing a user with a wireless access to external networks, hosts, or services offered by specific service providers. The user may need to have a subscribership with the mobile communications system in order to be able to use the services of the mobile system. The mobile subscription information of the subscriber may indicate parameters such as parameters regarding the quality of service (QoS) the subscriber is entitled to receive, priorities, service restrictions, security, authentications, and so on.
An access point or gateway node of the mobile communication network provides further access to an external network or an external host. For example, if the requested service is provided by a service provider located in another network, the service request is routed via a gateway to the other network and the service provider.
Various user equipment (UE) such as computers (fixed or portable), mobile telephones and other mobile stations, personal data assistants or organizers, and so on may be used for accessing packet switched services. Mobile user equipment, typically referred to as a mobile station (MS), can be defined as a means that is capable of communication via a wireless interface with another device such as a base station of a mobile telecommunication network or any other station. The increasing popularity of Third Generation (3G) communication systems will, in all likelihood, significantly increase the possibilities for accessing services on the packet data networks via mobile user equipment (UE) as well as other types of UE.
The term “service” used above and hereinafter will generally be understood to broadly cover any service or goods which a user may desire, require or be provided with. The term also will generally be understood to cover the provision of complementary services. In particular, but not exclusively, the term “service” will be understood to include browsing, downloading, email, streaming services, Internet Protocol (IP) multimedia (IM) services, conferencing, telephony, gaming, rich call, presence, e-commerce and messaging, for example, instant messaging.
A more detailed example of a wireless packet switched communication system will now be described with reference to general packet radio service (GPRS). The GPRS operational environment comprises one or more subnetwork service areas, which are interconnected by a GPRS backbone network. Each subnetwork may comprise a number of packet data service nodes (SN). In this specification the service nodes will be referred to as serving GPRS support nodes (SGSN). Each of the SGSNs is connected to radio networks, typically to base station systems and/or radio access networks by way of base station controllers (BSC) and/or radio network controllers (RNC) in such a way that they can provide a packet service for mobile user equipment via several base stations. The intermediate mobile communication network provides packet-switched data transmission between a support node and mobile user equipment. The subnetworks are in turn connected to an external data network, e.g. to a packet data network (PDN), via GPRS gateway support nodes (GGSN). The GPRS thus allow transmission of packet data between mobile user equipment and external data networks.
A packet data protocol (PDP) context may be established to carry traffic flows over the packet switched communication system. A PDP context typically includes a radio access bearer provided between the user equipment, the radio network controller and the SGSN, and switched packet data channels provided between the serving GPRS service node (SGSN) and the gateway GPRS service node (GGSN). A session between the user equipment and other party would then be carried on the established PDP context. A PDP context can carry more than one traffic flow, but all traffic flows within one particular PDP context are treated the same way as regards their transmission across the network. This requirement regarding the similar treatment is based on PDP context treatment attributes associated with the traffic flows. These attributes may comprise, for example, quality of service and/or charging and/or filtering attributes. From the above mentioned functions filtering generally refers to operations wherein it is checked if the address information in the data packet matches a filtering criteria. If a data packet passes the filter, the packet is allowed to be forwarded to a next router. If a data packet does not meet the predefined criteria, it is commonly dropped.
A policy controller entity, for example a policy decision function (PDF), can be provided for controlling the transport layer of a PDP context. The policy decision function (PDF) may be provided by any appropriate controller entity. The PDF and GGSN are commonly arranged to communicate information to enable co-operation between the GPRS bearer level and the IMS level of the communication system. The PDF may be used for storing attributes for the purposes of functions such as the Quality of Service, filtering of data packet in the GGSN and so on.
An IP Multimedia Service (IMS) session related set of binding information generated by a policy decision function (PDF) and sent via the user equipment, to the GGSN can be used to verify that the PDP context operations requested by the user equipment comply with the preceding negotiation on the IMS level during the set-up or modification of the PDP context. As a result of the verification, the PDF authorizes QoS parameters for the GGSN. The authorized parameters sent by the PDF to the GGSN may include, among other things, filter parameters known as Packet Classifiers. Packet Classifiers can be used by the GGSN to filter the user plane traffic, both uplink and downlink, in the relevant PDP context. Packet Classifier parameters are commonly derived from signalling, for example from SDP/SIP (Session Description Protocol/Session Initiation Protocol) signalling. Packet Classifiers may employ information about source address, source port, destination address, destination port and protocol.
When a user equipment sending data packets defines a route through the network, for example by using the Internet Protocol version 6 (IPv6) Routing Header, the user equipment may define additional routing information. For example, the sending user equipment may indicate a specific route that the data packets shall follow when communicated over the network. To implement this, it is possible to define the destination address in each data packet at the time of sending thereof such that the destination address of the data packet is the address of the next router in the selected route, and not the actual i.e. final destination address.
However, typically the filtering criteria is based on the address of the final destination. Thus the filtering criteria used by a Packet Classifier or any other appropriate filtering mechanism used by a node may not be based on the address of the next node but is instead based on the final destination address. That is, the filtering function of a node is not necessarily made aware that the destination address assigned for a data packet by a user equipment or a previous node is not the final destination address of that data packet. Thus the node would still apply a filtering criteria that is based on the final destination address on that data packet. As a result of this the filtering process may drop the packets because they do not match the filtering criteria. Thus the transmission of packets may fail.